Wireless in-kiln moisture sensor and system for use thereof

ABSTRACT

A wood monitoring system and method is disclosed for monitoring lumber characteristics (e.g., lumber moisture) in environments of extremely high and prolonged temperature and moisture, e.g., a kiln. The monitoring system and method includes:
         (a) Sensors (provided within lumber stacks), wherein such sensors are battery powered and wirelessly communicate measurements indicative of moisture content of the wood adjacent to and/or between metal plates provided in an electrical circuit with the sensors and the wood between the plates;   (b) Computer implemented methods and systems for wireless communication that conserve sensor battery power such that the sensors can operate for, e.g., six months within extremely adverse temperature and moisture environmental variations; and   (c) Computer implemented methods and systems for estimating moisture content with a wood/lumber stack, and for predicting such moisture content (e.g., as a substantially steady state within the wood) after drying completion.

RELATED APPLICATION

The present application is a continuation-in-part (CIP) application ofU.S. patent application Ser. No. 13/934,887, filed Jul. 3, 2013, whichclaims the benefit of U.S. Provisional Patent Application No. 61/667,942filed Jul. 4, 2012, each of which is fully incorporated herein byreference.

FIELD OF THE INVENTION

The present invention is related to the wireless monitoring of drying ofwood in a kiln, and more particularly, wireless sensors for monitoringthe wood drying process wherein the life of the batteries for thesensors is extended.

BACKGROUND

Today's market for kiln dried lumber demands significantly greaterattention to the lumber production process. Government and industryregulations and customer expectations of wood quality have increasedevery year. Additionally, competitive pricing of final lumber grade hasbecome more severe. Therefore, mills must maintain a high level ofscrutiny of each production stage to reduce or eliminate product errorsand waste. Process mistakes that do occur result in wood products thathave compromised strength properties, may be susceptible to mold, or canlose significant value due to shrinkage or any number of visual defects.In addition, wood processing errors can cause lost productivity as wellas higher energy costs for a mill.

There are a number of vendors that provide in-kiln moisture measurementsystems. In fact, prior art systems have been commercially available fortwo decades. Such prior art systems (e.g., by the manufacturers Wagner,Wellons, and Accudry, SCS Forest Products) have been described insignificant detail in various public disclosures, including thefollowing U.S. patent Nos.: U.S. Pat. No. 4,389,578 by Wagner; U.S. Pat.No. 4,580,233 by Parker, et al.; U.S. Pat. No. 6,703,847 by Venter etal.; and U.S. Pat. No. 6,989,678 by Venter et al. each of which is fullyincorporated herein by reference. Additionally, the following U.S.patent numbers are fully incorporated herein by reference: U.S. Pat. No.3,807,055 by Kraxberger; U.S. Pat. No. 4,107,599 by Preikschat; U.S.Pat. No. 6,124,584 by Blaker et al.; U.S. Pat. No. 6,281,801 by Cherryet al.; U.S. Pat. No. 6,784,671 by Steele, et al.; U.S. Pat. No.6,784,672 by Steele, et al.; U.S. Pat. No. 7,068,050 by Steele; and U.S.Pat. No. 7,068,051 by Anderson. U.S. Patent Application Publication No.US 2004/0187341 by Studd, et al. is also fully incorporated herein byreference.

All of these systems work using decades-old theory by convertingcapacitance response to moisture content. This is accomplished byplacing two or more metal plates in a lumber stack, which are verticallyseparated by some calculated distance. The system then creates acapacitor by applying an electrical signal to the plates. The maindipolar constituent between the plates is water within the lumber stack.Therefore, the capacitance response diminishes during a drying cycle aswater is removed. The drop in capacitance is correlated to the loss ofmoisture.

To-date, the prior art systems that perform the function of measuringthe change in capacitance over time, have relied upon placing one ormore fixed wall-mounted metering devices inside, outside or near thekiln for drying the lumber therein. The metering devices are responsiblefor determining the electrical response of the circuit formed by themetal (steel) plates and the lumber stack between the two plates. Cablesconnect the meters to the plates inserted in the lumber stack. Themetering devices, in turn, are connected, via wire or cables, to acentral programmable logic controller (PLC) or other computing device(e.g., a personal computer, PC herein). The calculation of moisturecontent is performed either at the meters themselves or at a central PLCor PC. These wired systems have been installed throughout lumber dryingkilns in North America.

These prior-art lumber drying systems have a number of limitations.Since all of these systems are connected via cables to a main PC orcontroller, the number of meters is limited by financial constraints. Inaddition to the per-unit cost for each meter, conduit runs must beinstalled to protect cables that transmit electrical measurements to thePCL or PC. Depending on the configuration of the kiln, these conduitruns can be hundreds of feet long. Running high temperature cable insidealuminum conduit between each meter and the PLC or PC is a considerableupfront expense as well as an on-going maintenance expense.

Another limitation of such prior art lumber drying monitoring systems isthat once a measurement point (e.g., meter) is fixed to the kiln walland conduit is run to that point, the location cannot be easily changedwithout incurring significant cost. Therefore, the operator does nothave flexibility to target desired locations in the kiln drying lumber.Often times, lumber mills will produce new lumber products that requiregreater in-kiln observation in the first number of manufacturing cycles.Installing additional moisture sensors in a timely manner is not anoption. Therefore, mills will often incur costly production loss andgreater energy usage in the early manufacturing runs until themanufacturing process has been standardized.

Finally, the entire lumber production industry is undergoing asignificant shift as the industry moves from batch processing of lumberto continuous processing. Instead of packages of lumber being placedinside a kiln for a set period of time, operators are continuouslymoving the stacks of lumber on rail tracks through various heatingchambers. Having measurement sensors within such lumber stacks whereinthe sensors are tethered to meters of fixed location is not an option inthis case. In particular, the lumber stacks may travel approximately 100feet (or greater, e.g., 200 feet) through the various drying chambers.At any one time, there may be 10 or more distinct lumber stacks movingthrough the drying process. Moving cables attached to each lumber stackwould create too many safety and logistical issues for the mills toconsider this a viable option.

Regarding wireless technology, unfortunately, commercially availablein-situ wireless moisture measurement sensors are not an option for anumber of reasons. First, there are no viable wireless systems that cansurvive softwood kiln temperatures. In most cases, kiln temperaturesreach 260° Fahrenheit (F) or higher, which is far higher thanconventional moisture sensor technology allows. Second, the kilnenvironment has very high humidity with hot ash and sap sticking to anyavailable surface. Because of these conditions, very limited electronicshave heretofore been provided inside the kiln. In particular, mostcommercially available electronics have a maximum temperature of 125° F.and are not effective for marine environments (e.g., where there isconsistently high moisture content of, e.g., 90% or more). Further,in-kiln temperatures can range from −40 to +260° F., and this widetemperature range is especially problematic in that kiln temperaturescan ramp from the low end of this range to the upper end of this rangein a matter of hours (e.g., three to four hours or less). Furthermore,sensors (in the lumber stacks) and the meters placed in the kiln mustoperate continuously for, e.g., up to three weeks.

Moreover, if the moisture sensors within the lumber stacks are to beuntethered (e.g., wireless) in their communications, then they must bepowered by batteries. However, in general, battery life for electronicdevices is severely degraded by the elevated kiln temperatures asrecited above. In fact, studies show that batteries operating attemperatures above 113° F. will lose 50% of their useful operating lifeperforming a task whereas at lower temperatures (e.g., 100° F.), therewould only be a 20% to 30% reduction in such useful operating life. Thisis particularly important for the drying and processing of softwoodlumber since such lumber may need to be monitored for lengthy timeperiods, e.g., approximately six months or longer in kiln environmentswith extremely high prolonged temperatures and/or extremely highprolonged moisture content. Accordingly, perhaps the most challengingfor wireless lumber monitoring sensors is the battery life. This isprobably the primary reason that no other manufacturer has developed awireless sensor based capacitance system for the monitoring the moisturecontent of softwood within wood drying kilns since softwood lumberin-kiln drying requires sensor batteries to be operationally useful atprolonged temperatures of 260° F. (or higher)—significantly higher thanthe top range for standard batteries to effectively operate, e.g., atypical wireless sensor. In particular, such high temperatures may berequired for up to twenty-one days. It is, however, worth mentioningthat there are specialty batteries that operate at higher temperatures,but battery life would still be a significant issue.

Because there are no wireless options for the softwood market, metersuppliers have looked at creating physical connections using sledsinstead of cables between the meters and the lumber stack. As the lumberstack moves past a fixed sled, the sensors within the lumber stack comeinto electrical contact (e.g., via a protrusion from each sensorcontacting sled) the meter can make a valid measurement. There are anumber of disadvantages with such sled systems, including, but notlimited to installment cost, maintenance costs, accuracy and limitedlumber moisture sampling ability due to the sleds being attached to thekiln wall. Accordingly, the adoption of these sleds has been very slow.

Due to the drawbacks (e.g., as recited above) with the prior art lumberdrying monitoring systems for the lumber industry, the technology in thepresent disclosure has been developed for addressing such drawbacks, andin particular, providing an apparatus (e.g., one or more computationaldevices/equipment) and computer methods for monitoring lumbercharacteristics (e.g., moisture content), wherein wireless lumbermeasurements are taken by sensors embedded within lumber stacks and suchsensors can remain operationally effective for extended periods of timewithout maintenance such as battery replacement.

Accordingly, it would be advantageous to have a lumber monitoring systemand method that mitigates or cures the above-identified drawbacks of thecurrent lumber drying systems and methods.

SUMMARY

A lumber monitoring system and method is disclosed hereinbelow formonitoring lumber characteristics (e.g., lumber moisture) inenvironments of extremely high and prolonged temperature and moisture.The present lumber monitoring system and method includes:

-   -   (a) Sensors (provided within lumber stacks), wherein such        sensors are (1) battery powered and wirelessly communicate        measurements indicative of, e.g., the moisture content of the        wood adjacent to and/or between metal plates provided in an        electrical circuit with the sensors and the wood between the        plates, and (2) able to effectively operate in such extreme        environments that vary from, e.g., from −40 to +260° F., with        ambient moisture content ranging from extended durations near        zero moisture to extended durations of 90% to 100% moisture;    -   (b) Computer implemented methods and systems for wireless        communication that conserve sensor battery power such that such        sensors can effectively operate for, e.g., six months within        extremely adverse temperature and moisture environmental        variations; and    -   (c) Computer implemented methods and systems for estimating        moisture content with a wood/lumber stack, and for predicting        such moisture content (e.g., as a substantially steady state        within the wood) after drying completion.

In one embodiment of the presently disclosed system and associatedmethod, the lumber monitoring equipment (including associated computersystems for performing various computations) can be configured formeasuring attributes or characteristics of lumber prior to, during andafter such lumber is processed within, e.g., a lumber drying kilnfacility and/or another lumber processing facility such as a saw mill.In particular, such lumber attributes or characteristics are monitoredso that the lumber's environment (e.g., in kiln environment) can beadjusted and/or maintained so that the lumber attains (and retains) adesired range of moisture content. Such lumber monitoring equipment maydetermine appropriate lumber moisture content ranges, wherein suchranges may be dependent upon, e.g., the type of wood, the currentcontent of moisture, expected environmental conditions to which thelumber may be subjected, etc. Such monitoring equipment typicallyincludes a PLC or PC (as these terms are defined above) having variousspecialized computer programmatic instructions for (a) controlling thewood monitoring process and (b) computing, e.g., estimated current woodmoisture content and/or predicting a resulting substantially steadystate moisture content within the wood after drying. Note that thehardware and software for performing (a) and (b) immediately above alsowill be referred to hereinbelow as a “controller”.

The novel lumber monitoring system and method of the present disclosureprovides a unique solution that limits battery usage by sensors, e.g.,within lumber stacks. In particular, the following features areprovided:

-   -   (a) Each such sensor only wirelessly transmits (to a wireless        device identified as a “hub” or “hub device” herein) when        capacitance within the lumber stack (within which the sensor is        embedded) has changed by a predetermined amount (e.g. a        percentage thereof), and    -   (b) Each such sensor wirelessly reduces the number of readings        and wireless transmissions during less critical phases and        increases the read rate and wireless transmissions when these        readings are most important.        In particular, embodiments of the lumber monitoring equipment        and associated method therefor increase battery performance such        that empirical testing shows batteries can potentially last six        months or more in a typical operating environment within a        lumber drying kiln.

Another novel aspect of the present disclosure includes computerinstructions (and/or dedicated computational machine device(s)implementing such instructions in hardware and/or software) forestimating moisture content using both capacitance and resistance. Inparticular, the present disclosure describes the creation and use of aunique index (Measurement Index herein) for assessing moisture contentin lumber, wherein both capacitance and resistance are provided asinputs, and such inputs may be combined or weighted for estimating themoisture content in lumber. For example, at one or more time intervals(e.g., during the drying of lumber), resistance measurements are givenan increased weight in the Measurement Index in comparison tocapacitance measurements. In particular, capacitance is not as accurateas resistance at high moisture readings. However, as lumber dries, ithas been determined that capacitance becomes far more accurate thanresistance in measuring lumber moisture content. Thus, alternatingcurrent (AC) resistance measurements can be a good indicator of moisturecontent when wood is very wet since, e.g., large changes in resistancemay be the result of small changes in moisture content while capacitancemeasurements are more indicative of wood moisture content when suchmoisture content is below, e.g., a range of fiber saturation point asone skilled in the art will understand. Therefore, the novel wood dryingsystem and method models the wood drying process much more consistentlyand accurately when both capacitance and resistance are used.

Embodiments of the present wood drying system and method also providefor the wireless monitoring of wood moisture content. Further, suchwireless monitoring can be performed in:

-   -   (1) A batch mode where the wood in a given batch is dried        separately from other batches, or    -   (2) A continuous mode where wood for various products is dried        concurrently, albeit according to each product specifications;        in particular, such continuous wood drying includes the movement        of the stacks of wood between drying chambers.

It is also an aspect of the presently disclosed monitoring system thatthe wireless sensors used for such monitoring can be easily repositionedas desired for better monitoring the moisture content of the wood forthe product intended. Moreover, it is within the scope of the presentlydisclosed wood monitoring system to allow various sensors to bewirelessly activated and deactivated by, e.g., a hub device with which aplurality of such sensors wirelessly communicate. Accordingly, wirelesssensors may be distributed throughout a wood stack, and one or more ofthe sensors may be activated in response to, e.g., data received from asubset of the sensors. In particular, a PLC or PC performing thecomputations for converting received sensor data (obtained via one ormore hub devices, likely at fixed locations along the wood/lumberprocessing or drying path) may determine whether sensor data fromadditional sensors within a wood stack should be activated.

It is a further aspect of an embodiment of the presently disclosedmonitoring system that such a PLC or PC has access to mapping data whichindicates the locations of the sensors within the wood/lumber stack. Inone embodiment, each sensor may be wirelessly located within its woodstack and/or relative to other sensors so that a data map of the sensorswithin the wood stack can be generated and used for selectivelyactivating and/or deactivating various sensors (subsets thereof)depending on the sensor's location within its stack (or more generallyin the kiln), and/or wood monitoring data received from, e.g., aparticular subset of the sensors. In one embodiment, disjoint subsets ofsensors may be activated and deactivated throughout the storage andprocessing of a wood/lumber stack (i.e., while being dried in a kiln,being stored after or before drying, being processed after being dried)for determining the moisture within the wood. Such disjoint subsets ofsensors may provide the following advantages: (1) the battery life ofeach sensor is extended since its subset is only activated occasionally,(2) if each sensor subset is distributed differently but still is ableto provide monitoring data for the entire wood/lumber stack, then thevarious sensor views of, e.g., moisture within the wood/lumber stackfrom the various sensor subsets can provide greater assurance that thewood/lumber is being properly processed and/or maintained, and (3) thesensor subsets provide a failsafe ability to the monitoring process inthat one or more failed sensors may be tolerated due to the plurality ofviews of the wood/lumber provided by multiple sensor subsets.Accordingly, the PLC or PC (referred as a “controller” hereinbelow) mayperform such selective activation and/or deactivation via wirelesstransmissions to the sensors activated or deactivated.

In one embodiment of the presently disclosed monitoring system, thepositions of the sensors within a wood/lumber stack are determinedrelative to one another, relative to another location, or as an absolutelocation (e.g., via GPS). Accordingly, the presently disclosedmonitoring system can detect an unintended dislocation of a sensorrelative to other sensors, and adjustments may be made in the monitoringof the wood/lumber and/or an operator may be alerted to, e.g.,reposition the dislocated sensor.

Since lumber drying kiln operators can deploy as many of the presentlydisclosed measurement sensors as required for the specific wood productbeing produced, in some cases, mills may add, subtract or repositionsensors within a wood stack between kilns to provide improved samplingin a particular kiln. Note that since various kilns may havesubstantially different wood drying characteristics (e.g., heat flowpatterns, heat gradients, air circulation, and venting) suchrepositioning of sensors may be dependent upon the kiln within which thewood stack is provided. Additionally/optionally, a plurality of sensorsubsets may be provided in the wood stack so that one or more sensorsets may be activated dependent upon the particular kiln in which thewood stack having the sensor subsets is provided.

Moreover, in one embodiment of the presently disclosed monitoringsystem, the number, location and/or activation of sensors within a woodstack also can be dependent upon the type of wood. Some wood/lumberproducts can be more variable in their moisture content within a wooddrying kiln. In particular, additional moisture content sensor datasamples may be needed to fine tune the wood drying process. In otherwood/lumber products being dried, the wood/lumber moisture content maybe more evenly distributed; thus fewer sensors (or activations thereof)may be required to make (1) an accurate prediction of the currentmoisture content of a wood stack, and/or (2) make a prediction of whatthe moisture content of the wood stack will be after drying (assuming,e.g., the wood stack is stored or processed in a manner that is amenableto such prediction).

It is a further aspect of the wood sensors disclosed herein that theyhave a reduced susceptibility to corrosion from the drying of wood. Inparticular, such sensors are subjected to potentially corrosivesubstances in wood ash and sap. Note, it is well known that wood iscorrosive by nature and can be made more corrosive by varioustreatments. In particular, wood includes acetic acid which is volatile,and in an ill-vented space (such as in a kiln), wood can cause metalcorrosion; further, wood ash includes from 0.2 to 4% of mineral ash,which consists largely of calcium, potassium and magnesium as carbonate,phosphate, silicate, and chloride; aluminum, iron and sodium are alsopresent. Sulphate contributes 1 to 10% of wood ash by weight, andchloride 0.1 to 5%, and these two radicals augment the corrosive actionof the acetic acid.

Accordingly, embodiments of the wood monitoring system and method hereinmay provide the following benefits:

-   -   1. Since the hub(s) need not be tethered to the sensors, such        hub(s) can be flexibly located inside or outside the kiln from        which the hub(s) receive wireless sensor transmissions. In        particular, such hub(s) need only be able to wirelessly        communicate with the sensors and also transmit data (e.g., via a        cable) to the controller (as this term is described above).        Thus, such hub(s) need only be placed in wireless range for        communicating with the sensors in the kiln associated with        hub(s). Thus, such hubs may be positioned in a mill yard,        sawmill, planer mill, etc. That is, the hub devices are no        longer limited to being located in the kilns. Also, since such        hub devices can be positioned virtually anywhere along a wood        processing path (e.g., within a saw mill), real-time monitoring        of wood moisture content can be determined where heretofore such        has not been possible.    -   2. When a sensor's battery potential reduces below, e.g., a        predetermined threshold, the frequency of data transmissions may        be reduced to conserve the battery.    -   3. In one embodiment, the controller is provided with data        indicative of critical wood drying intervals for a wood stack.        Accordingly, the controller may instruct the sensors within the        wood stack to reduce their moisture sampling rates outside of        such critical intervals to thereby extend the sensors' effective        battery life. Note that such critical intervals may be based on        historical wood/lumber drying for the type of wood/lumber being        currently kiln dried, and/or the particular kiln being used for        the drying, and/or the kiln settings (e.g., timing of heat        applied, venting, circulating fans activated, etc.).    -   4. More accurate and reliable moisture content estimation is        achieved by using both capacitance and resistance to estimate        wood/lumber moisture content as discussed hereinabove.    -   5. The sensors have a reduced susceptibility to wood product        corrosion.

In one embodiment, the present disclosure is directed to a method formonitoring the moisture content of a collection of wood members (e.g.,lumber) drying in a kiln, the kiln operable for applying heat, and aircirculation for drying the collection to a specified moisture content,wherein:

-   -   There is a wireless sensor in operable contact with the wood        collection for forming an electrical circuit with the wood,        wherein the circuit additionally includes two spaced apart        conductive plates positioned within the wood collection, and        wherein the sensor and the circuit are configured to establish        each of a capacitance and resistance of a water content of at        least a portion of the collection, the portion residing between        the spaced apart conductive plates; and    -   wherein the sensor includes: (a) a wireless transmitter for        wirelessly communicating with a stationary device, the        stationary device for wirelessly receiving data from the sensor        related to the water content of the portion of the collection,        the data including measurements of the capacitance and        resistance, and (b) one or more batteries for providing        electrical power to the sensor;    -   wherein the method performs the following steps by computational        machinery:        -   (a) activating a timer for determining when a first time            limit is exceeded;        -   (b) obtaining an instance of the data during the first time            limit;        -   (c) determining a value indicative of a change between the            instance and a previous instance of the data;        -   (d) comparing the value to a predetermined change related            condition indicative of particular changes between instances            of the data;        -   wirelessly transmitting the instance to the device, via the            wireless transmitter, when the comparing step yields a first            result indicative of the predetermined change related            condition occurring between the one instance and the            previous instance, and not wirelessly transmitting the            instance when the comparing step yields a second result            indicative of the predetermined change related condition not            occurring between the one instance and the previous            instance;        -   wirelessly transmitting a further instance of the data to            the device, via the wireless transmitter, when the first            time limit is exceeded;        -   (e) evaluating a predetermined condition, wherein the            evaluation of the predetermined condition performs one            of: (i) a comparison of an elapsed time for drying the            collection in the kiln with a predetermined elapsed time            limit for drying the collection in the kiln, (ii) a            comparison of a humidity in the kiln with a humidity            threshold, or (iii) a comparison of an impedance for the            portion of the collection with an impedance threshold;        -   (f) obtaining, when the predetermined condition evaluates to            a predetermined result, information for a second time limit            different from the first time limit;        -   (g) using the information for activating the timer to            determine when the second time limit is exceeded; and        -   (h) wirelessly transmitting a second instance of the data to            the device, via the wireless transmitter, when the second            time limit is exceeded;    -   wherein for conserving the batteries, the first time limit is        longer than the second time limit.

In a related embodiment, the present disclosure is directed to awireless sensor for monitoring the moisture content of a collection ofwood members (e.g., lumber) being dried in a kiln, the kiln operable forapplying heat, and air circulation for drying the collection to aspecified moisture content, wherein the wireless sensor is in operablecontact with the wood collection for forming an electrical circuit withthe wood, wherein the circuit additionally includes two spaced apartconductive plates positioned within the wood collection, and wherein thesensor and the circuit are configured to establish capacitance andresistance of a water content of a portion of the collection, theportion residing between the spaced apart conductive plates; the sensorincluding:

-   -   (a) one or more batteries for electrically powering the sensor;    -   (b) a wireless transmitter for wirelessly communicating with a        stationary device, the wireless communications including        transmissions by the transmitter of data related to the water        content of the portion of the collection, the data including        measurements of each of the capacitance and resistance,        measurements of the humidity in the kiln, and measurements of a        temperature in the kiln;    -   (c) a processor for iteratively: (i) obtaining one of the        measurements of the capacitance, one of the measurements of the        resistance, one of the measurements of the humidity, and one of        the measurements of the temperature, and (ii) providing the one        measurement of each of: the capacitance, resistance, humidity        and temperature to the wireless transmitter for wirelessly        transmitting as an instance of the data;    -   (d) a timer for determining when a first time limit is exceeded;        -   wherein one of the instances of the data is obtained by the            processor during the first time limit;        -   wherein the processor obtains a value indicative of a change            between the one instance and a previous instance of the            data;        -   wherein the processor compares the value to a predetermined            change related condition for identifying specific changes            between instances of the data, and thereby obtaining one of:            a first result indicative of the predetermined change            related condition occurring between the one instance and the            previous instance, and a second result indicative of the            predetermined change related condition not occurring between            the one instance and the previous instance;        -   wherein the wireless transmitter wirelessly transmits the            instance to the device when the first result is obtained,            and does not wirelessly transmit the instance when second            result is obtained;        -   wherein the wireless transmitter wirelessly transmits a            further instance of the data to the device when the first            time limit is exceeded;        -   wherein the processor evaluates a predetermined condition,            the evaluation of the predetermined condition performs one            of: (i) a comparison of an elapsed time for drying the            collection in the kiln with a predetermined elapsed time            limit for drying the collection in the kiln, (ii) a            comparison of a humidity in the kiln with a humidity            threshold, or (iii) a comparison of an impedance for the            portion of the collection with an impedance threshold;        -   wherein the processor obtains, when the predetermined            condition evaluates to a predetermined result, information            for a second time limit different from the first time limit;        -   wherein the processor uses the information for activating            the timer to determine when the second time limit is            exceeded;        -   wherein the wireless transmitter wirelessly transmits a            second instance of the data to the when the second time            limit is exceeded;        -   wherein for conserving the batteries, the first time limit            is longer than the second time limit.

This Summary section is neither intended to be, nor should be, construedas being representative of the full extent and scope of the presentdisclosure. Additional benefits, features and embodiments of the presentdisclosure are set forth in the attached figures and in the descriptionhereinbelow, and as described by the claims. Accordingly, it should beunderstood that this Summary section may not contain all of the aspectsand embodiments claimed herein.

Additionally, the disclosure herein is not meant to be limiting orrestrictive in any manner. Moreover, the present disclosure is intendedto provide an understanding to those of ordinary skill in the art of oneor more representative embodiments. Thus, it is important that theembodiments herein be regarded as having a scope including constructionsof various features of the present disclosure insofar as they do notdepart from the scope of the methods and apparatuses consistent with thepresent disclosure. Moreover, the present disclosure is intended toencompass and include obvious improvements and modifications of thepresent disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a vertical cross section through a priorart lumber kiln moisture system, wherein a kiln for drying lumber isshown having a lumber stack therein, and the stack has spaced apartmetal plates inserted therein. Each of the metal plates is tethered to akiln wall mounted meter for obtaining, e.g., capacitance and resistancemeasurements indicative of the moisture content of the lumber betweenthe metal plates. Accordingly, such prior art meters perform theprocessing provided herein by the novel sensors 20 (FIG. 2). However,since the wood/lumber stack is tethered to the wall of the kiln, thestack cannot be moved without disconnecting the cables from the meter.Moreover, the moisture in the wood/lumber stack can only be monitoredwhere such a meter is in close proximity for connecting the cablesthereto.

FIG. 2 shows a vertical cross section through an embodiment of a novelwireless in kiln lumber monitoring system according to the presentdisclosure.

FIG. 3: is a block diagram showing the major system components.

FIG. 4: is a block diagram showing the components of the wirelessmoisture sensor.

FIG. 5: is a block diagram showing the components of the wireless hub.

FIG. 6: is a flow chart describing the logic used to conserve battery ina wireless sensor 20. In this case, transmissions are reduced by onlytransmitting when certain conditions have been met.

FIG. 7: is a flow chart describing the logic used to conserve batterypower in a wireless sensor 20. In this case, the moisture readings arereduced.

FIG. 8: is a circuit diagram.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 2 and 3 illustrate embodiments of the lumber monitoring system andmethod as configured in a typical lumber mill. The main components arethe wireless sensors 20, the wireless hubs 24 (also referred to as “hubdevices” hereinabove and below) and a controller 28. Although only threesensors 20 are illustrated in FIG. 3 as residing in each of the stacks32, this is only for illustrative purposes. In general, a substantiallylarger number of sensors 20 may be distributed within a correspondingwood/lumber stack 32 for collecting, e.g., wood/lumber capacitance andresistance data related to the moisture content of the stack 32. Each ofthe sensors 20 wirelessly communicates with a corresponding hub 24 fortransmitting, e.g., the following data to the corresponding hub 24:

(1) a sensor 20 identifier (for identifying each sensor 20 uniquely),

(2) capacitance and resistance data indicative of the moisture contentin the stack 32,

(3) measurements indicative of remaining battery power.

Other data values transmitted to its corresponding hub 24 (andsubsequently transmitted to the controller 28) are disclosed in AppendixA hereinbelow).

Note that the sensors 20 are preferably distributed within or about thestack 32 according to a known configuration that may be based on: (a)the wood type in the stack 32, (b) an indication/estimation of woodmoisture, and/or (c) characteristics of the kiln itself (as discussed inthe Summary section hereinabove). More particularly, as shown in FIG. 2,each sensor 20 may be attached, via cables 34, to a unique pair of metalplates 36 (in some embodiments, a single cable 34 is connected to justone of the metal plates 36 with the other metal plate 36 beinggrounded), this pair being referred to herein as being “associated” withits sensor 20. The metal plates 36 are spaced apart within thewood/lumber stack 32, generally in a vertical direction; however theymay be spaced apart horizontally as well. The associated pair of metalplates 36 is used to provide its sensor 20 with electrical propertiesrelated to the wood/lumber residing between these metal plates, and moreparticularly, information indicative a capacitance and resistance of thewood/lumber between these metal plates. A description of the use of suchcapacitance and resistance for determining the moisture content of thewood/lumber by the sensor 20 is provided in Appendix A hereinbelow.Related discussions of the use and computation of wood moisture contentis provided in, e.g., various U.S. patents such as some of those recitedabove, and more particularly, U.S. Pat. No. 7,676,953 (the '953 Patentherein) assigned to Signature Control Systems, Inc. which is also fullyincorporated by reference herein.

The sensors 20 offer substantially more flexibility in monitoring woodmoisture over prior art systems having a “meter” attached to the kilnwall as shown in FIG. 1. Since the sensors 20 are each wireless, eachsuch sensor can be transported with the wood/lumber stack 32 withoutconnecting and disconnecting cables. Thus, such sensors 20 and theirassociated cables 34 and metal plates 36 can be attached to theirwood/lumber stacks 32 prior to the stack entering the kiln, and canremain with the stack after the kiln drying process is complete tothereby continue to monitor the moisture in the stack if desired.

Various configurations of the sensors 20 (and their associated metalplate 36 pairs) may be provided within a wood/lumber stack 32. In oneembodiment, a first row of the sensors 20 may be distributed, evenlyspaced, in (or about) the stack 32 substantially around a horizontalperimeter of the stack at a first height relative to the stack (e.g., ator near the top of the stack as illustrated in FIG. 2), wherein for eachof the sensors 20, its associated metal plate 34 pair is approximatelyadjacent to its sensor 20, and such that this sensor is operablyattached to (or contacting) the stack 32 in a manner that allows thissensor to, e.g., determine a local humidity of the air adjacent to thissensor, and determine a local temperature adjacent to this sensor whichis indicative of at least one of: the wood/lumber at the sensor 20 orthe air temperature thereabout. Since the spacing of the metal plates 36within the stack 32 is likely to be no more than six to eight feet (andpossibly substantially less), depending on, e.g., the height of thestack 32, a copy of the first row of sensors 20 (and their associatedmetal plate 34 pairs) may be provided as a second row of sensors 20wherein this second row is provided at a different height relative tothe stack. In particular, the first row of sensors 20 may be near or atthe top of the stack 32, and the second row may be positioned below thefirst row an effective distance so that the sensors can reliably collectcapacitance and resistance data for the wood between correspondingvertically aligned metal plate 36 pairs associated with each of thesensors 20 (e.g., without electrical interference from another sensorand its associated metal plate 36 pair. Since the wood/lumber stack 32may be as much as 12 feet high, a plurality of instances of the firstand second sensor rows may be provided in the stack at spaced apartvertical intervals. Note that the sensors 20 and the wireless hubs 24for wirelessly communicating therewith (such sensors 20 and their hub 24referred to herein as “corresponding” herein) may wirelessly communicateaccording to any one of the conventional wireless communicationprotocols such as WIFI, Bluetooth and any other protocol of a wirelessfrequency as allowed by law as one of ordinary skill in the art willunderstand.

The controller 28 may be connected to each of the wireless hubs 24 via acable or wire (illustrated as a double headed arrow in FIG. 3 andidentified as a cable in FIG. 2). Although two hubs 24 are shown in FIG.3 as communicating with the controller 28, such a controller can be insignal communication with only one hub 24 or a relatively largeplurality of hubs 24 (e.g., 15 to 30 meters or more). In one embodiment,the controller 28 may be collocated with one of the hubs 24. Thecommunication between a controller 28 and a hub 24 is two-way to therebyenable, e.g., (1) sensor data (obtained by the hub 24 from correspondingwireless sensor 20 transmissions) to flow from the hub to thecontroller, and (2) controller 28 commands to be transmitted to the hub24 and its corresponding sensors 20 (with which the hub wirelesslycommunicates) for controlling both the hub and such sensors 20. In oneembodiment, the wired or cable connection between a hub 24 and thecontroller 28 is via an Ethernet cable run in conduit as one skilled inthe art will understand.

FIG. 3 also illustrates an embodiment where there is an exchange ofinformation between the hubs 24 themselves (e.g., via wirelesscommunications such as WIFI or Bluetooth, or an Ethernet cableconnection) as illustrated by the double headed arrow between the twoillustrated hubs 24. Such communication between hubs 24 allows thesehubs to be daisy-chained so that data can be sent from hub to hub (e.g.,for a potentially large number of hubs such as twenty hubs).Accordingly, when the hubs 24 are daisy-chained, the direct connectionbetween, e.g., the hub in kiln #2 and the controller 28 can be dispensedwith if the hub 24 in kiln #1 is configured to transfer designatedcommunications between the hub 24 of kiln #2 and the controller 28.Assuming such a daisy-chain configuration includes wirelesscommunications between the hubs 24, such a configuration may limit thecost of the present wood monitoring system by reducing the amount ofconduit that must be run for providing communications between thecontroller 28 and the plurality of hubs 24 operably controlled by thiscontroller.

Hubs 24 may be located on the outside of a kiln having sensors 20corresponding to the hub. The number of hubs 24 per kiln may bedetermined by the size and/or design of the kiln. For typical batchkilns, (e.g., kilns that dry all the wood in the kiln according to asingle drying method where all the wood is moved into the kiln prior tokiln operation for drying the wood, and all wood in the kiln is movedout of the kiln only after all the wood is dried), one hub 24 may beplaced in a location amenable for effective wireless communications withall the sensors 20 in the kiln. However, depending on the wirelessenvironment, e.g., within the kiln, additional hubs 24 may bedistributed about the kiln.

The wireless sensors 20 attached to a wood stack 32 can be grouped. Thehighest grouping typically will include all the sensors 20 residing in asingle stack 32, or if the kiln is a batch kiln, all the sensors 20residing in the kiln. Subgroupings or subsets (as discussed hereinabove)may be provided. Each sensor 20 in a group (or subset) wirelesslytransmits data to a single predetermined corresponding hub 24. Eachgroup of sensors 20 may monitor a single kiln or a chamber within akiln; however, a single stack 32 also may be monitored. When a hub 24receives data from its corresponding sensors 20, the hub will, in turn,put the data in a buffer and subsequently relay the data to thecontroller 28. Once the data is received by the controller 28, thecontroller stores the data in a database (not shown). Note, although notshown in FIG. 3, the sensor data may be displayed to an operatoraccessing the controller 28 so that the operator can monitor the wooddrying process in substantially real-time.

In an embodiment, the case of the kiln may be molded (e.g., usingplastic injection molding) to allow the movement of the antennas (e.g.,the hub antenna 72) to move inside the box (e.g., for improved receptionwith the sensor antenna). The case of the kiln may also be made of othermaterials (e.g., metal such as aluminum).

FIG. 4 shows a high level embodiment of a sensor 20. The sensor 20includes a micro-processor 40 having firmware installed therein forperforming at least the following tasks: (i) transmitting stack 32moisture related data, e.g., when such data has changed in somemeaningful way, and (ii) changing the moisture data sampling rate, e.g.,the sample rate may be reduced during “non-critical” wood dryingstages). Both of these aspects are described in more detail below.

The sensor 20 further includes the following components (each suchcomponent may be an integrated circuit more commonly known as a chip):

-   -   (a) An ID component 44 which may be a programmable EPROM or        other silicon based component for storing identification data.        The ID component 44 outputs, when requested by the        micro-processor 40, identification data that uniquely identifies        the sensor 20 from all other sensors 20.    -   (b) An analog measurements component(s) 48 which may be        impedance chip AD5934 by Analog Devices, Inc., One Technology        Way, Norwood, Mass. 02062-9106 (USA). The analog measurements        component(s) 48 receives input from: (i) a temperature        measurement component 48 a (e.g., the AD5934 chip above also has        an embedded temperature sensor). Further, the analog device        component 48 determines capacitance and resistance electrical        measurements corresponding to a moisture in the drying wood        between the associated metal plates 36 for this sensor 20.        -   Regarding capacitance and resistance measurements, the            analog measurements component(s) 48 determines capacitance            measurements according to the disclosure in Appendix A            provided hereinbelow.    -   (c) A humidity component 52 which may be a relative humidity        sensor such as model number HTS2030SMD by Measurement        Specialties, Inc., 1000 Lucas Way Hampton, Va. 23666 (USA). The        humidity component 52 outputs, on request from the        micro-processor 40, a measurement of the ambient humidity at the        sensor 20.    -   (d) One or more batteries 54 for providing electrical power to        the components of the sensor 20.    -   (e) An analog-digital converter component 56 which may be a        micro-processor from the SAM4L family of microcontrollers by        Atmel Inc., 1600 Technology Drive, San Jose, Calif. 95110 (USA).        The analog-digital converter component 56 receives analog        electrical signal input from the battery 54 indicative of the        useful additional life in the battery for powering the sensor        20. In one embodiment, the output from the battery 54 may be a        current measurement or a voltage. Upon request from the        micro-processor 40, the analog-digital converter 56 outputs        digital data corresponding to the input received from the        battery as one skilled in the art will understand.    -   (f) A wireless transceiver component 64 which may be a radio        transceiver or transmitter by

Micrel, Inc., 2180 Fortune Drive, San Jose, Calif. 95131 (USA), modelnumber: P/N MICRF405YML operating at 900 MHz. Upon receiving an outputdata packet from the micro-processor 40, the wireless transceivercomponent 64 wirelessly transmits the data packet to the hub 24 to whichthe sensor 20 corresponds. A wireless transceiver 68 and antenna 72(FIG. 2) in the hub 24 receives the wireless data packet.

At certain designated times (or time intervals) while wood/lumberin-kiln drying is proceeding, the micro-processor 40 requests andreceives data from each of the following components: the ID component44, the analog measurements component(s) 48, the humidity component 52,and the AD (analog to digital) component 56. Once the data has beenreceived from each of these components, the information is assembledinto a data packet and provided to the wireless transceiver component 64for wireless transmission to the hub 24 corresponding with the sensor20.

For generating a data packet, the micro-processor 40 requestsinformation from the components 44 through 56. Subsequently, themicro-processor 40 receives from the ID component 44, hexadecimal sensoridentification data that uniquely identifies the sensor 20. Theidentification data is transmitted to the hub 24 with every data packetgenerated by the micro-processor 40 for identifying the source sensor ofthe data. For each data packet generated, preferably, themicro-processor 40 also obtains output from the analog measurementscomponent(s) 48. As described above, the analog measurementscomponent(s) 48 measures capacitance, resistance and temperature, and atleast for the capacitance and resistance value, calibration valuesprovided by the micro-processor 40 are used, wherein such calibrationvalues are well known in the art for calibrating capacitance andresistance of the wood between the metal plate 36 pairs connected to thesensor 20. The calibration values are used by the analog measurementscomponent(s) 48 to reduce or substantially entirely factor outextraneous capacitance and resistance values not indicative of thewood/lumber between the metal plate 36 pair associated with the sensor20. In particular, for the electrical circuit 70 (FIG. 2) of the sensor20, the attached cable(s) 34, the associate metal plate 36 pair, and thewood/lumber between these metal plates 36, the calibration values areused to remove, or substantially reduce, from the capacitance andresistance measurements, factors such as the capacitance and resistanceof the cables 34 so that the capacitance and resistance values output bythe analog measurements component(s) 48 to the micro-processor 40substantially are only indicative of the moisture in the wood/lumberbetween the metal plates 36 associated with the sensor 20.

Additionally, the micro-processor 40 obtains from the humidity component52 the relative humidity of the ambient air surrounding the sensor 20for also providing in each generated data packet. Finally, an analog todigital component 56 is utilized to calculate a digital value of thevoltage level of the batteries 54 and such calculated voltages areprovided to the micro-processor 40 for inclusion in each data packet.

For a given collection of data from the components 44, 48, 52, and 56(the data obtained for a same time), the micro-processor 40 generates acorresponding data packet that includes the content of the collecteddata. Note, that the micro-processor 40 includes a timing component(e.g. firmware), well-known in the art, for programmatically determiningwhen to request and collect the data from the components 44, 48, 52, and56. The timing component can be modified by commands from the controller28, wherein such modifications may be:

-   -   (1) for setting a time interval between data collections from        the components 44, 48, 52, and 56 (and substantially immediate        transmissions of the corresponding resulting data packet to the        controller 28, via wireless transmission to the hub 24),    -   (2) for setting a range for at least one value from the        collected data, wherein if the at least one value is outside of        the range, then subsequent data collections are performed at a        different frequency (e.g., a greater or lesser frequency as may        be determined by communications from the controller 28,    -   (3) setting different frequencies for collecting data from the        components 44, 48, 52, and 56; for example, if the sensor's        battery is low and it is not expedient to replace the battery or        provide another proximate sensor 20 in the near term (e.g., due        to the sensor 20 being not easily accessible), then unless a        wood drying anomaly is detected, the sensor may conserve battery        power by the micro-processor 40 only obtaining data input from a        subset of the components 44 through 56 for at least some        instances of the data packets generated and transmitted.

Note that in one embodiment, some of the components 44, 48, 52, and 56may not be included in the sensor 20. In particular, in one embodiment,the humidity component may not be provided. Instead, humidity data maybe obtained separately from the sensors 20, and communicated to thecontroller 28. Moreover, in one embodiment, the sensor 20 may alsoinclude an acoustic component for capturing particular sounds associatedwith the drying of wood such as wood cracking, shifting, and/or warping,etc. Accordingly, data from such an acoustic component can be alsocollected and provided in the micro-processor generated data packet fortransmission to the controller 28.

In one embodiment, the hub 24 and each of its corresponding sensors 20(plus possibly other sensors 20 whose wireless transmissions the hub candetect) may communicate asynchronously (or substantially so) ondifferent wireless frequencies. Accordingly, there is little likelihoodof collisions of data packets at the hub 24. However, since there may bea large plurality of sensors 20 (e.g., 20 or more) corresponding withthe hub 24 for asynchronous wireless communication therewith, theadditional hub and sensor electronics (and corresponding cost thereof)for allowing wireless communications between the hub 24 and each of itscorresponding sensors 20 to occur on distinct wireless frequencies maybe cost prohibitive in at least some embodiments. Thus, in analternative embodiment, a predetermined small number of wirelessfrequencies may be utilized for communication between the hub 24 and itscorresponding sensors 20. In this alternative embodiment, when asensor's wireless transceiver component 64 receives a data packet fromthe sensor's micro-processor 40, the component 64 wirelessly transmitsthe data packet repeatedly; e.g., the data packet may be transmitted atthree randomly determined times. Sending each data packet randomly three(or more) times is believed to substantially assure each data packetfrom the sensor 20 is accurately received by the associated hub 24 suchthat wireless transmissions by other sensors 20 do not interfere withwireless reception by the hub 24 of transmissions by the present sensor.Note that since each data packet has a unique timestamp, any duplicatecopies of a data packet received by a hub 24 can be deleted.

FIG. 5 illustrates the high level componentry of the hub 24. In additionto the antenna 72 and the transceiver 68, each hub 24 also includes:

-   -   (a) An ID component 76 which may be a programmable EPROM or        other silicon based component for storing identification data        uniquely identifying the hub 24 from all other hubs. The ID        component 76 outputs, when requested by the micro-processor 88        (described below), the identification data to the        micro-processor 88.    -   (b) A temperature measurement component 80 for outputting        temperature values as requested by the micro-processor 88. Note        that since this portion of the hub 24 is outside of the kiln,        this temperature measurement component 80 measures the        temperature outside the kiln, and such measurements can be        useful for the controller 28 to control the wood/lumber drying        process within the kiln, and in particular, control the        activation of one or more of the heaters in the kiln, kiln        intake and exhaust fans, and fans for circulating air within the        kiln as one skilled in the art will understand.    -   (c) A data storage 84 (which may be persistent for storing        data). This data storage 84 is used to store data packets (or        data therefrom) received from the sensors 20.    -   (d) A micro-processor 88 for storing and accessing data packets        received from sensors 20, and for generating, on request from        the controller 28, aggregated data for sending to the controller        28. In particular, the micro-processor aggregates the following        for sending to the controller 28: (1) one or more data packets        from one or more sensors 20, (2) the unique hub identifier from        the ID component 76 for uniquely identifying the hub, and (3)        one or more temperature measurements from the temperature        measurement component 80 (with corresponding time stamps).    -   (e) Various components used for digitally transmitting the        aggregated data to the controller 28, such component may include        one or more of: an RS-232 port 92, and an RS-422 port 96        together with a converter 100 for the RS-422 port as one skilled        in the art will understand.

As mentioned previously, each hub 24 may be mounted outside its kiln ina location effective for communicating wirelessly with the hub'scorresponding sensors 20 (e.g., within the kiln). Each hub 24 has anantenna 72 and a hub transceiver 68 that may be in the interior of thekiln so that the hub can better receive wireless transmissions from thecorresponding sensors inside the kiln. Thus, as shown in FIG. 2, part ofthe hub 24 can be interior to the kiln (to which the hub is attached)and part of the hub can be external to the kiln. The antenna 72 andwireless transceiver 68 captures the wireless transmission of the datapackets from the wireless sensors 20 and provides the captured datapackets to the hub's micro-processor 88. The micro-processor 88 storesthe data packets in RAM 80 until the micro-processor 88 receives arequest from the controller 28 to send the stored data packets to thecontroller. Once such a request is received by the hub 24, themicro-processor 88 retrieves the data packet(s) from the RAM 80, asksthe ID component on board for the unique tag, obtains a reading from thelocal temperature component and then sends the aggregated data stream tothe controller 28 via an RS422 or RS232 port.

In an embodiment, the board may be coated (e.g., using silicone, vapordeposition, and/or other coatings) for better protection from theenvironment and other reasons.

FIG. 6 shows two high level flowcharts for limiting the number ofwireless transmissions from each sensor 20 to its corresponding hub 24and thereby conserving the batteries 54. The kiln environment isexceptionally harsh with temperatures regularly exceeding 200° F. forperiods ranging from 16 to 48 hours or more. At these temperatures, thebatteries 54 will experience a substantial reduction in life incomparison to a more typical battery environment as discussed above. Forthis reason, battery consumption must be conserved as much as possible.

Since the transceiver component 64 of each sensor 20 consumes the mostsensor 20 battery power, a method for reducing the number of wirelesstransmissions without sacrificing critical data transfers to thecorresponding hub 24 is provided in FIG. 6. In particular, theflowcharts of FIG. 6 provides the steps performed by the softwareexecuted by the micro-processor 40 or the controller 28 for comparingcurrent sensor 20 readings to past readings (for the same sensor 20) inorder to determine if a change in the moisture content data transmittedfrom this sensor warrants a more frequent or less frequent sensorwireless data transmission rate. Since what is deemed to be criticalor/and not critical, changes per kiln operator, one or more setpointsfor changing such transmission rates can be specified by, e.g., anoperator (or automatically via computer instructions). Note that suchsetpoints may be dependent upon various wood/lumber dryingcharacteristics, e.g., in-kiln temperature, sensor reading of resistanceor capacitance, etc. Once such a setpoint is established, the sensor(s)20 affected will only send updates to its corresponding hub 24 when themaximum or minimum corresponding conditions for the establishedsetpoint(s) has been reached. As a fail-safe, there is a maximum timelimit between transmissions that is allowed, so even if a sensor'sgenerated output data has not changed, the sensor will still transmitwood/lumber drying related data packets to its corresponding hub 24.

Assuming the micro-processor 40 in the sensor 20, performs the steps ofthe flowcharts of FIG. 6, is the micro-processor 40 has a built-in timer(not shown) that counts the seconds (or fractional increments thereof)until the micro-processor 40 initiates a next collection ofmeasurements/readings from the sensor components 44 through 56 (FIG. 4).The timer may have a default time interval of, e.g., 5 minutes betweensending notifications so that the micro-processor 40 requests (inresponse to each notification) output data from the components 44through 56. However, this time interval may be changed depending on thebattery 56 remaining life, the wood/lumber drying measurements (or achange thereof), kiln operator input, and/or controller 28 computationsof a new time interval. Accordingly, referring to the rightmostflowchart of FIG. 6, in step 604, once this timer has entirely counteddown its time interval (or alternatively, if the timer is counting up toits time interval's end, then when the timer exceeds the time interval'send, as one skilled in the art will understand), the micro-processor 40receives a “time interval expired” notification from the timer, and inresponse, the micro-processor 40 (step 608) sends a request to each ofthe components 44 through 56 (FIG. 4) to output their correspondingmeasurements/readings to the micro-processor 40. Upon receiving themeasurements/readings, the micro-processor 40 (step 612) determines ifit has exceeded the maximum time limit between wireless transmissions ofdata packets to its hub 24, wherein this maximum time limit is, in oneembodiment, a time limit corresponding with one of the “fast mode” orthe “slow mode” discussed hereinbelow with reference to FIG. 7. Notethat the time interval used for determining the expiration in step 608may be different from the maximum time limit. In particular, the timeinterval is substantially fixed and short enough so that the highestexpected frequency of data packet generation and wireless transmissionfrom the sensor 20 (equivalently, the smallest maximum time limit value)can be maintained. In particular, the time interval used in step 604 maybe identical to the maximum time limit of the “fast mode” describedhereinbelow.

Accordingly, if the maximum time limit of step 612 is exceeded, then themicro-processor 40 generates a new data packet from the newly receiveddata obtained from components 44 through 56 (step 616). Subsequently, instep 620, this newly generated data packet is stored to a buffer (notshown) in the transceiver component 64 for transmission (step 624) tothe corresponding hub's antenna 72 and wireless transceiver 68.Subsequently, in step 628, the timer is reset and the process startsover.

However, if in step 612, the maximum time limit between wirelesstransmissions is not exceeded, then in step 632, the steps of theleftmost flowchart of FIG. 6 are performed, wherein in step 636, themicro-processor 40 retrieves the previous measurement data obtained fromthe components 48 through 56 from its memory (not shown), and inputs thenew and old measurements/readings (e.g., the capacitance, resistance,temperature and humidity values) to a calculation (step 640) selectedby, e.g., the kiln operator (or the controller 28) to determine whethercertain conditions, e.g., of the wood/lumber (between the metal plates36 associated with the sensor 20), are satisfied. For example, suchconditions may be for detecting a change in the capacitance and/orresistance of the wood/lumber being monitored. In particular, one ormore of the three immediately following calculations may be performed bythe micro-processor 40 to determine a change in capacitance orresistance and subsequently determine whether a certain condition, usingthis change value, is satisfied (e.g., predetermined conditions and theparticular “change” calculation may be specified by the operator and/orthe controller 28):

-   -   1. Calculate a rate of change of the capacitance and/or        resistance of the wood/lumber between the metal plates 36        associated with the sensor 20.    -   2. Calculate an absolute change, e.g., the positive value        difference between the new value and the old value of the        capacitance and/or resistance. of the wood/lumber between the        metal plates 36 associated with the sensor 20    -   3. Calculate the percent of change: the absolute difference        between the new value and the old value divided by the old value        of the capacitance and/or resistance of the wood/lumber between        the metal plates 36 associated with the sensor 20.        However, it is also within the scope of the present disclosure        that other measurements of wood/lumber capacitance and/or        resistance may be calculated in additional to or instead of        those of (1)-(3) immediately above. Moreover, selected        calculations corresponding to in-kiln temperature and/or        humidity can also be used in evaluating conditions related        thereto. Thus, for temperature, one of the following        calculations may be performed for a given temperature related        condition:    -   4. Calculate a rate of change of the temperature of the        wood/lumber in proximity to the sensor 20.    -   5. Calculate an absolute change, e.g., the positive value        difference between the new value and the old value of the        temperature of the wood/lumber in proximity to the sensor 20.    -   6. Calculate the percent of change: the absolute difference        between the new value and the old value divided by the old value        of the temperature. of the wood/lumber in proximity to the        sensor 20.

Similarly, selected calculations corresponding to in-kiln humidity canalso be used in evaluating conditions related thereto. Thus, forhumidity, one of the following calculations may be performed for a givenhumidity related condition:

-   -   7. Calculate a rate of change of the humidity of the wood/lumber        in proximity to the sensor 20.    -   8. Calculate an absolute change, e.g., the positive value        difference between the new value and the old value of the        humidity of the wood/lumber in proximity to the sensor 20.    -   9. Calculate the percent of change: the absolute difference        between the new value and the old value divided by the old value        of the humidity of the wood/lumber in proximity to the sensor        20.

Once the selected calculations of (1)-(9) have been performed, then instep 644, the micro-processor 40 compares the results from thecalculations of step 640 with one or more corresponding thresholds setby the operator (by the controller 28 without operator selection of suchcalculations) for determining if one or more of the certain conditionsassociated with these thresholds are satisfied. For example, for athreshold of 2 units corresponding to calculation an absolute change inthe stack moisture content of step 640, if the result from thecalculation is below the threshold, then it is presumed that thewood/lumber between the metal plates 34 associated with the sensor 20 isrelatively dry. Additional such examples are as follows:

-   -   For a threshold of 5 degrees, corresponding to an absolute        change in temperature, if the sensor 20 registers a change        greater than this threshold, then it is presumed the ambient        temperature in the kiln (e.g., at least proximate to the sensor        20) has sufficiently changed to warrant an update to the kiln        operator.    -   For a threshold of 100%, corresponding to the percent of change        in humidity, if the sensor 20 registers a change greater than        this threshold, then it is presumed the ambient humidity in the        kiln (e.g., at least proximate to the sensor 20) has        sufficiently changed to warrant an update to the kiln operator.        Accordingly, if the micro-processor 40 determines that no        threshold is crossed by the corresponding result (calculated in        step 640) to which the threshold is compared thereby indicating        that the corresponding condition for the threshold is not        satisfied, then no data packet is generated for wireless        transmission and the method of FIG. 6 starts over. However, if        one of the thresholds is crossed, then steps 616 through 628 are        performed for generating and wirelessly transmitting a new data        packet to the corresponding hub 24. Thus, the wireless        transceiver component 64 is only activated for performing        wireless transmissions when the micro-processor 40 detects a        change in one or more of the values output by the components 48        through 56 that are deemed significant to trigger the wireless        reporting of this change to the corresponding hub 24 (and        subsequently by this hub to the controller 28). Accordingly, the        batteries 56 have their life extended by the process of FIG. 6.

Description of FIG. 7.

Referring now to FIG. 7, in a typical wood/lumber in-kiln drying cycle,the wood/lumber starts out very wet with moisture content in the 60%+range by weight. Accordingly, a kiln operator(s) will typicallyinitially ramp up the kiln temperature relatively high (e.g., in therange of 220° F. to 260° F.) and also adjust air speed inside the kilnin an effort to dry the lumber in a uniform manner Readings from amoisture meter are typically used at this stage to guide this initialdrying cycle as illustrated in FIG. 1. The operator(s) may also adjustsome of the macro-conditions in the kiln (e.g., kiln vents, etc.) sothat the wood/lumber finishes this initial drying cycle at 19% or lessmoisture content by weight. As the wood nears 19% in moisture content,the operator(s) may focus his/her attention on previously determined orhistorical correlations between characteristics of the dryingwood/lumber and in-kiln environmental characteristics (such correlatesreferred to as a “drying curve”) for achieving a targeted range ofmoisture content in the drying wood/lumber. For example, suchcorrelations may relate, e.g., (i) the type of lumber, the amount oflumber in the kiln, and/or the stacking configuration of the lumber,with (ii) in-kiln temperature, in-kiln air circulation speed, kiln ventconfigurations, and/or the length of time at certain kiln dryingconfigurations. Thus, the kiln operator(s) typically closely monitoreach of the wood/lumber stack embedded sensors 20 in order to target apredetermined average lumber moisture content of, e.g., 19% or less.Moreover, as the moisture content to the drying wood/lumber gets closeto the targeted lumber moisture content (e.g., 5% higher than thetargeted lumber moisture content), the time between updated moisturerelated sensor values becomes more critical since one or two percentchanges in wood moisture content can dramatically affect final productquality. Thus, such sensor 20 values need not be uniformly determinedand transmitted for estimating lumber moisture content.

Thus, in order to manage and substantially lengthen the battery life ofbatteries 54 in sensors 20, a unique method for reducing the powerconsumed by the various components in such sensors has been developedand is disclosed herein with reference to FIG. 7. In particular, FIG. 7provides a flowchart of the steps performed for setting the read rate(i.e., a wireless transmission rate) for each sensor 20 to either a“fast” wherein data packets are generated and wirelessly transmittedmore frequently, or a “slow” mode wherein data packets are generated andwirelessly transmitted less frequently. That is, each of the fast modeand the slow mode has a corresponding time limit value which isindicative of the maximum time between wireless transmissions of datapackets to the hub 24, wherein this maximum time is shorter for the fastmode, and longer for the slow mode (e.g., five minutes for the fast modeand fifteen to twenty times for the slow mode). Note, as indicatedhereinabove, the maximum time limit used in step 612 of FIG. 6 is themaximum time limit of whichever of the fast and slow modes is currentlybeing used by the micro-processor 40.

During the early phases of a drying cycle, each sensor 20 defaults tothe “slow” mode in which data packet wireless transmissions areperformed, e.g., every 15 minutes. When particular conditions aresatisfied at a sensor 20, the micro-processor 40 of the sensor 20switches to a “fast” mode wherein the wireless transmission rate of datapackets increases to, e.g., every 5 minutes. In this way, battery 54power consumed by all the components of the sensor 20 can be reducedsince such components are activated less often during the initialportion of a drying cycle since the sensor is in slow mode.

In one embodiment, there are three possible trigger values to switch asensor 20 from the slow mode to the fast mode. The three trigger valuesare of the following types:

-   -   i. Charge timer: A kiln operator (or the controller 28 exclusive        of the operator(s)) can set a time (e.g., the number of hours)        after the start of the drying wood/lumber drying process to        switch from slow to fast mode, or possibly vice versa.    -   ii. Humidity level: The kiln operator can set a threshold        corresponding to a particular relative humidity level in the        kiln so that when this threshold is reached, the sensor 20 will        switch from slow to fast mode. In the early phases of a kiln        drying process, the humidity inside the kiln is very high as        water is extracted from the wood/lumber and this extracted water        disperses as moisture in the kiln air. Later in the wood/lumber        drying process, there is less remaining water in the        wood/lumber, and accordingly, the humidity levels in the kiln        fall.    -   iii. R value level (i.e., an impedance threshold of the circuit        70 for the sensor 20): This value is a complex resistance value        that can be used to judge the relative moisture content of the        wood between the two metal plates 36 associated with the sensor        20. Low resistance indicates wet wood.        Each of these triggers may set remotely from the sensor 20 and        transmitted wirelessly (via the sensor's corresponding hub 24)        to the sensor for use by the sensor's micro-processor 40 in        performing the flowchart of FIG. 7.

Accordingly, the steps of FIG. 7 determine the time interval used by thetimer discussed hereinabove in describing FIG. 6. That is, the timeinterval (either for fast mode, or slow mode) determined in FIG. 7 isused to determine when the timer expires in step 604 (FIG. 6)

Referring now to the steps of FIG. 7, for a given sensor 20 these stepare described as follows:

-   -   Step 700: A determination is made as to whether the fast mode        has already been set; i.e., the timer interval has been set to        its shortest duration. If so, then FIG. 7 terminates since in        the present embodiment, since once the fast mode is set it is        set for the duration of the drying process.    -   Step 704: Assuming the fast mode has not yet been set, in the        present step, the micro-processor 40 of the sensor receives        measurements/readings from the sensor's components 48 and 52        (i.e., obtaining capacitance, resistance values of the circuit        70 (FIG. 2) having the sensor therein, and a relative humidity        value output by the humidity component 52). Note that the        capacitance and resistance values obtained are used to obtain        the R value trigger type as shown in Appendix A.    -   Step 708: The micro-processor 40 determines whether a charge        timer value has been communicated from the controller 28 to the        sensor for currently being used as trigger for changing, e.g.,        from the slow mode to the fast mode.    -   Step 712: If a charge timer has been set, then the        micro-processor 40 accesses an elapsed time since the kiln        drying process commenced for determining whether the charge        timer designated elapsed time has been exceeded. Note that the        time at which in-kiln wood/lumber drying commenced can be        communicated from the controller 28 to each of the sensors 20 in        the kiln. Accordingly, as one skilled in the art will        understand, each sensor's micro-processor 40 can use its own        clock to iteratively determine elapsed times of the drying        process.    -   Step 714: If the determination in step 712 is positive, then the        maximum time limit for step 612 (FIG. 6) is set (by the        micro-processor 40) to the value for the fast mode instead of        the initial slow mode, e.g., the maximum time limit is reduced        from, e.g., 15 minutes to 5 minutes    -   Step 718: The timer (or some timer operably associated with the        micro-processor 40) is activated for commencing to determine        when a next instance of the maximum time limit is exceeded so        that the micro-processor 40 (for this sensor 20) can be notified        to provide a new data packet to the transceiver 64 for        wirelessly transmitting to the corresponding hub 24 as per steps        615 through 624 of FIG. 6.    -   Step 722: After step 718, the present step is iteratively        performed for determining whether the current maximum time limit        is exceeded by its timer (assuming the timer is counting up to a        designated time value indicative of the time interval offset, or        alternatively, if this timer counts down the time interval, when        the timer expires). Once the present step results in a positive        determination, then step 700 is again performed.    -   Step 724: A determination is made as to whether a humidity level        trigger has been set by the kiln operator (or the controller 28        independent of the operator).    -   Step 728: If a humidity level trigger has been set, then the        micro-processor 40 accesses an the humidity level trigger value        and a current humidity value obtained from the humidity        component 52 for determining whether the humidity level trigger        value has been exceeded by the current humidity value. If yes,        then steps 714 through 722 are performed as described above. If        not, then step 732 following is performed.    -   Step 732: A determination is made as to whether an R value level        trigger has been set by the kiln operator (or the controller 28        independent of the operator).    -   Step 736: If an R value level trigger has been set, then the        micro-processor 40 accesses an the R value level trigger value        and a current impedance (for the sensor's circuit 70) obtained        from the analog measurements components 48 for determining        whether the R value level trigger value has been exceeded by the        current impedance value. If yes, then steps 714 through 722 are        performed as described above. If not, then steps 718 and 722 are        performed.

FIG. 7 is particularly useful for kiln operators that want to increasethe transmission of wireless sensor data packets after a certain numberof hours has transpired, regardless of other ambient conditions. Thereason that the operators are likely want such increases in transmissionrate is that mills may want to begin a detailed examination of thedrying rate early in the drying process in order to manage kiln fans andheating. Many mills believe such management improves final driedwood/lumber quality. Other mills may use such an increase intransmission rate as a backup in case other environmental conditions arenot met. So, if a predetermined number of hours of a kiln wood/lumberdrying process has transpired, no matter what, the mill may wish toincrease the transmission rate to provide more data packets to thecontroller 28 and the operator.

In a further embodiment, additional control (e.g., software) may be usedto control the kiln. For example, Kilnscout is an advanced, wirelesssensor that records moisture content, temperature, humidity, and windvelocity to determine the optimum push rate for drying lumber. Thesensor itself transmits this data to a central computer program foranalysis. In addition, the central software collects other informationfrom the kiln. This includes push rate, temperature drop across the load(TDAL), moisture data from the in-line planer systems, and varioustemperature and humidity sensors in fixed locations throughout the kiln.The software uses all of these inputs to determine proper push rate foroptimum results. It employs a feedback loop for real-timemicro-adjustments to push rate.

It is noted that push rate drives overall productivity for lumberproducers. Slower rates cause production to decrease. Increased ratesimprove productivity, but can cause quality concerns. Therefore, it is acontinuous struggle to find the optimum production rate. Added to thiscomplexity is the ever-changing nature of incoming wood andenvironmental conditions throughout production.

KilnScout is a rugged, wireless sensor that is placed in a lumber kilnto measure moisture content, temperature, humidity, and wind velocity.It measures data in fixed time increments. At the conclusion of ameasurement cycle, it sends the data to receiver hubs located on thekiln walls. This data is pushed to a computer in the control room. Keydata is stored in SQL to be shared with various other internal andexternal systems. Users can set parameters so that data received thatare outside certain control limits can trigger alerts via text, emailand on-screen notifications. Information from other systems also reportto KilnScout. Examples include temperature, humidity, temperature dropacross loads, push rates, species, spot check quality control data, etc.All of this is combined with internally generated data to create aprofile of the lumber drying in the kiln. Thresholds for certain datacan be created so that the system can make intelligent decisions on whento increase the push rate for lumber so that drying times can bereduced. Feedback is constantly received so micro-adjustments can bemade in real-time. The feedback loop is important as variation in theprocess and material must be recognized and overcome.

Important to all of this are features for alerting and messaging. Asdescribed above, text, email, and on-screen notifications are central tothe success of the system. Users look to optimize results and expect thesystem to perform. Any deviation in expected outcome of quality and/orproduction can be quickly identified and acted upon.

Deficiencies in the related art include not enabling users to quicklyand accurately assess conditions inside a lumber kiln. Continuous kilnsare even more difficult to understand. Users rely upon fixed meters onthe side of the kiln walls to make judgments on production quality.These fixed meters include temperature and humidity. All of these metersgather indirect atmosphere measurements that are used to infer thematerials' actual state as it moves through production.

Using KilnScout, the user can measure the material directly. The sensormoves with the material through the production process. Measurementsfrom the sensor, combined with readings from other external meters onthe kiln, are collected by KilnScout's software program. The softwaredetermines optimum process rates by analyzing all of the available data.No longer is the process a black box for the user as key data iscontinuously displayed on a PC.

The present disclosure has been presented for purposes of illustrationand description. Further, the description herein is not intended tolimit the present disclosure to the form disclosed herein. Consequently,variation and modification commiserate with the above teachings, withinthe skill and knowledge of the relevant art, are within the scope of thepresent disclosure. The present disclosure is further intended to enableothers skilled in the art to utilize the present disclosure, or otherembodiments derived therefrom, e.g., with the various modificationsrequired by their particular application or uses of the presentdisclosure.

APPENDIX A Introduction

This Appendix describes the use, operation and the circuit model of thesensor 20.

Sensor 20 Operation

There are two pushbuttons on the sensor 20, each with a red LED in thecenter.

-   -   POWER button (left) Holding this button for over 1 second        toggles power on and off    -   CONTROL button (right) Used to trigger a measurement, initiate        calibration, clear flags, and enter or leave test mode.        The pushbuttons can sense “clicks” and “holds.” A “click” is a        quick button press (0.1 to 0.5 sec), and a “hold” is a single        button press that lasts longer than 1 second. The number of        sequential clicks is counted by the microcontroller and used to        select various functions.

LED flashes are brief (20 ms) to minimize power consumption.

For the impedance determined by one of the analog measurementscomponents 48, there are the following:

-   -   An analog input for impedance measurement.    -   An impedance output from the analog measurements component 48        for measuring impedance, e.g., from a sine wave generator output        for such impedance measurements.    -   Sensor antenna which may be a ¼ wave wire antenna.

Control Button and LED

A control button (not shown) is provided on the sensor 20; the button isused as follows:

-   -   1 click Force immediate impedance measurement followed by 3        radio transmissions over the next 30 to 40 seconds.    -   4 clicks Initiate impedance calibration. A 10K calibration        resistor must be connected across the measurement terminals.        Calibration will not occur if the calibration resistor is not        connected.    -   6 clicks Clear flag byte. This clears the over/under-temperature        flags and low battery flag. The “calibration valid” flag is not        affected.

The sensor 20 includes a control LED status light (not shown). Operationof the control LED is as follows:

-   -   1 Flash An impedance measurement has been made. Three random        radio transmissions will follow to the corresponding hub 24 for        wirelessly transmitting a data packet thereto.    -   2 Flashes Power just turned off.    -   3 Flashes Power just turned on.    -   4 Flashes Calibration was successful.    -   6 Flashes Flag byte was cleared.    -   Long flash Just entered test mode.

Power Button and LED

The sensor 20 includes a power button (not shown); operation of thisbutton is as follows:

-   -   Hold Toggle power on and off.        -   If power is off, a hold of the power button causes the            control LED to flash 3 times. Power to the sensor 20 is now            on.    -   If power is on, a hold of the power button causes the control        LED to flash 2 times. Power to the sensor 20 is now off.

There is a power LED on the sensor 20. The following are indicated bythis LEC:

-   -   1 Flash Occurs every 4-5 seconds when power is on.    -   3 Flashes Just left test mode.

Radio Data Packets

The sensor 20 measures complex currents, battery voltage, andtemperature every, e.g., 5 minutes (or as instructed by the controller28) and transmits the results to its corresponding hub 24. In oneembodiment, the transceiver component 64 sends one type of data packet,length 46 bytes, which contain the following information:

-   -   LEN (1 byte) Total data length in bytes, including this byte and        CRC. Always 0x2E.    -   ID (4 bytes) Unique sensor 20 identifier.    -   Resistance (8 bytes) Eight measurements are provided:        -   R1H, R1L 1953.1250 Hz at high amplitude (R1H), 1953.1250 Hz            at low amplitude (R1L);        -   R2H, R2L 2929.6875 Hz at high amplitude (R2H), 2929.6875 Hz            at low amplitude (R2L);    -   Capacitance (8 bytes) Eight measurements are provided:        -   C1H, C1L 1953.1250 Hz at high amplitude (C1H), 1953.1250 Hz            at low amplitude (C1L);        -   C2H, C2L 2929.6875 Hz at high amplitude (C2H), 2929.6875 Hz            at low amplitude (C2L);    -   FLAGS (1 byte) Flag byte. Bits are as follows:        -   D0 1=low battery level (4.00V) occurred (for the batteries            54).            -   Cleared by the following actions to the sensor 20:                power-on reset, pushbutton reset, and “clear flags”                command issued by the controller 28 to the sensor 20.        -   D1 1=sensor 20 calibration invalid.        -   Cleared when calibration sensor 20 has been completed and is            valid.        -   D2 1=fast (1-minute) impedance sampling by the sensor 20 in            normal mode.            -   0=normal (5-minute) sampling of impedance by the sensor                20.            -   Can only be set or cleared when the sensor 20 is in test                mode.        -   D3, D4 reserved, always 0 at this time.        -   D5 1=The temperature measurement at the sensor 20 dropped            below −40 C. The controller 28 clears this data field by            issuing a “clear flags” command to the sensor.        -   D6 1=temp exceeded 125 C. Cleared by “clear flags” command            from the controller 28 to the sensor 20.        -   D7 1=temp exceeded 130 C. Cleared by “clear flags” command            from the controller 28 to the sensor 20.    -   VBATT (2 bytes) Battery 54 voltage in units of 10 mV. This data        field is an unsigned integer. Each measurement for this field is        made during an impedance measurement (by the analog measurements        component(s) 48) while battery current drain is at maximum.    -   TEMP (2 bytes) Temperature in degrees C. with 1-degree        resolution at the sensor 20. This data field is a signed        integer.    -   CRC (2 bytes) CRC. This is used by the controller 28 to verify        that the serial data channel from the radio receiver has no        errors. The radio receiver always checks that there are no radio        channel errors.

Radio transmissions from the sensor 20 are repeated randomly three timeswith 11-14 seconds delay between, each transmission. Repeatedtransmission of the same data packet improves the probability of itbeing received by the sensor's corresponding hub 24 in the presence ofmultiple wireless transmissions from other sensors 20, radio fading,etc. In one embodiment, the corresponding hub 24 transfers each datapacket instance received to the controller 28, the sensor ID, and atimestamp to avoid duplicately processing a data packet, or to detectthat a measurement has been missed.

CRC Calculation

Data types used in the following code example are:

UINT8 unsigned integer 8-bit UINT16 unsigned integer 16-bit UINT32unsigned integer 32-bit

The following code takes the receiver packet buffer PktBuffer[ ] andcalculates the 16-bit CRC:

UINT32 PktCRC; // Shift register for CRC calculation. // Bits 0x00ffff00of PktCRC are the 16-bit CRC.//********************************************************* // FunctionpktGetCRC( ) // Calculate the CRC of the received packet.//********************************************************* UINT16pktGetCRC ( // Return the 16-bit CRC result.    UINT8 PktBuffer[ ]) //Received packet. {    UINT8 i, j;    if (PktBuffer[0] != 0x2E) // Exitof packet length is wrong.       return 0;    PktCRC = 0; // Zero theCRC.    j = PktBuffer[0] − 2; //Number of bytes to process for CRC.   for (i=0; i<j; i++) { // Process all bytes before the message CRCbytes.       pktByteCRC(PktBuffer[i]); // Update CRC for each byte.    }   pktByteCRC(0); // Process 0's in place of the CRC bytes of thepacket.    pktByteCRC(0);    return (UINT16)( (PktCRC >> 8) & 0xFFFF ) ;} //********************************************************* //Function pktByteCRC( ) // Update the CRC for one packet byte.//********************************************************* voidpktByteCRC( // Update the CRC for one byte of the packet.    UINT8 byte)// Data byte from packet. {    UINT8 i;    PktCRC &= (UINT32)0x00ffff00;// Clear low byte.    PktCRC |= (UINT32)byte; // Bring in the new databyte.    for (i=0; i<8; i++) { // Process 8 new bits into the CRC.   PktCRC <<= 1; // Shift all.    if (PktCRC & (UINT32)0x01000000) // If1 was shifted out,       PktCRC {circumflex over ( )}=(UINT32)0x00102100; // Apply inversions.    } }The result should equal the 16-bit CRC from the received packet.

Impedance Calculation

The sensor 20 (more particularly, the analog measurement component 48for obtaining impedance related values) applies to the circuit 70 a sinewave voltage to an induced predetermined impedance, and measures theresulting AC current of the circuit 70 through this impedance. Thesensor 20 does not calculate the impedance itself. Rather, it makes acomplex measurement of the AC current and provides the real andimaginary components thereof to the controller 28. The phase of thecurrent is also measured relative to the phase of sine wave generator inthe analog measurement component 48.

Complex current measurements are made at two different frequencies,1953.125 Hz and 2929.6875 Hz as discussed above. At each frequency,measurements are made at a high amplitude (for impedances >=10K) and alow amplitude (for impedances 1K to 10K). Calibration measurements arealso made at both frequencies and both amplitudes.

During calculations, the controller 28 checks the magnitude of thecomplex current. If the magnitude is too high during the high-amplitudemeasurement, the measurement circuit may have been clipping. In thatcase, the low-amplitude measurement must be used instead. In particular,if the high-amplitude measurement has a magnitude over 15500, use thelow-amplitude measurement.

The circuit diagram illustrated in FIG. 8 is used as a model for thecircuit 70, wherein the external impedance in the diagram is thewood/lumber between the metal plates 36 associated with the sensor 20.

Referring to the circuit diagram illustrated in FIG. 8:

-   -   Fixed circuit values used are:        -   Ro=2000 ohms Circuit output resistance        -   Co=0.22 uF Circuit output capacitance    -   The measurement frequency value must be used when converting        between reactance and capacitance. The impedance of a capacitor        is defined as imaginary and negative, which means the current        phasor through a capacitor is imaginary and positive (current        leads voltage).

Xc=−1/(2πFC)

C=1/(2πF(−Xc))

Zc=−jXc

-   -   -   Xc Capacitive reactance in ohms        -   Zc Complex impedance of a capacitor        -   C Cap in Farads        -   F Freq in Hz

    -   Parallel/Series conversions are required to calculate the        external impedance Ze are as follows (the identifiers in the        circuit diagram illustrated in FIG. 8 (and following): ending in        “p” denote parallel measurements, and ending in “s” denote        serial):

Rp=(Rs ² +Xs ²)/Rs

Xp=(Rs ² +Xs ²)/Xs

Rs=RpXp ²/(Rp2⁺ Xp ²)

Xs=Rp ² Xp/(Rp ² +Xp ²)

-   -   -   Rs, Cs External series equivalent resistance and capacitance        -   Xs External series equivalent reactance        -   Rp, Cp External parallel equivalent resistance and            capacitance

Xp=−1/(2πF Cp) External parallel equivalent reactance

-   -   Equations used in the calculations are:

Xo=−1/(2πF Co) Circuit output reactance

Zo=Ro+j Xo Circuit Output Impedance

Ze=Rs+j Xs External impedance

Ze=[Rp Xp ²/(Rp ² +Xp ²)]+j[Rp ² Xp/(Rp ² +Xp ²)]

Z=Zo+Ze Total impedance

I=V/Z Complex current

V=I Z Complex drive voltage

Note, the calculations in this Impedance Calculation section may beperformed by the analog measurements component(s) 48, and in oneembodiment, by the impedance chip from Analog Devices, Inc.

Calibration

For calibration of the sensor 20, a 10K ohm resistor is connected and acalibration sequence is initiated. The sensor 20 measures the AC currentthrough this resistor and stores the real and imaginary results. Thesecalibration measurements are included in every data packet along withmeasurements for the unknown impedance.

During calibration, the controller 28 first uses the calibration currentmeasurement, Ical, and the total calibration impedance, Zcal, tocalculate the complex excitation voltage V as follows:

Rp, Cp External components connected in parallel during calibration

Ze=[Rp Xp ²/(Rp ² +Xp ²)]+j[Rp ² Xp/(Rp ² +Xp ²)] External impedanceduring calibration

Zcal=Zo+Ze Total impedance during calibration

Ical Complex current measured during calibration

V=Ical Zcal Complex drive voltage

This complex V is constant and can be used in the calculations ofunknown impedances. Four values of V may be calculated at eachmeasurement frequency and at each amplitude. Capacitive reactancechanges with frequency, and the internal phase shift of the sine wavesource changes with amplitude.

The measurement units of I are not important, since V is calculated fromI and so the units of V will be correct for calculating impedances inohms as long as Zcal is calculated in ohms.

Measuring External Rp, Cp

Measurement involves connecting an unknown external Rp and Cp, measuringI, and using the known value of V to calculate Rp and Cp.

I Complex current measured

-   -   If abs(I) >15,500 then make the results Rp, Cp invalid. This        will occur at high output amplitude when small external        impedance is connected and indicates that the AD5933 A/D        converter is clipping.

Z=V/I Total impedance with unknown Rp, Cp

-   -   If abs(I)<0.5 (complex I measurement is zero) then limit        Z=1e8+0i to prevent overflows.

Ze=Z−Zo External impedance with unknown Rp, Cp

Rs=re(Z)−Ro External series resistance

Xs=im(Z)−Xo External series reactance

Rp=(Rs ² +Xs ²)/Rs External parallel resistance

-   -   Use the absolute value of Rp to cover cases where Rs is small        and negative (re(Z) is close to Ro). Limit Rp to 10M ohms        maximum to cover cases where Rs is very small.

Xp=(Rs ² +Xs ²)/Xs External parallel reactance

-   -   Use the absolute value of Xp to cover cases where Xs is small        and negative (im(Z) is close to Xo).

Cp=1/(2πF(−Xp)) External parallel capacitance

-   -   Limit Cp to the range 0.1 pF to 0.1 uF to cover cases where Xp        is very large or small.        If the flag byte (described above) indicates that the sensor 20        is uncalibrated, then the Rp and Cp results are invalid.

Wireless Setup Battery Installation and Sensor 20 Startup

The following procedure is for installing the batteries 54 in the sensor20 and then activating the sensor.

-   -   Open the sensor 20 back cover and install two batteries 54. The        batteries are both oriented in the same direction as marked on        the battery holders. Incorrect installation will not damage the        sensor 20, but it will not operate.    -   Press the “RESET” button on the PCB and check that the CONTOL        LED flashes twice.    -   Hold the POWER button until the CONTOL LED flashes 3 times.        Power is now turned on and the unit will transmit measurements        every 5 minutes.

1-19. (canceled)
 20. A method for monitoring the moisture content of acollection of wood members drying in a kiln, the kiln operable forapplying heat, and air circulation for drying the wood collection to aspecified moisture content, wherein a wireless sensor in operablecontact with the wood collection for forming an electrical circuit withthe wood collection, wherein the circuit additionally includes twospaced apart conductive plates positioned within the wood collection,and wherein the sensor and the circuit are configured to establish eachof a capacitance and resistance of a water content of at least a portionof the collection, the portion residing between the spaced apartconductive plates; and wherein the sensor includes: (a) a wirelesstransmitter for wirelessly communicating with a stationary device, thestationary device for wirelessly receiving data from the sensor relatedto the water content of the portion of the collection, the dataincluding measurements of the capacitance and resistance, and (b) one ormore batteries for providing electrical power to the sensor; comprisingperforming the following by computational machinery: activating a timerfor determining when a first time limit is exceeded; wirelesslytransmitting a first instance of the data to the stationary device, viathe wireless transmitter, when the first time limit is exceeded;evaluating, based on the data, a predetermined condition, wherein theevaluating of the predetermined condition comprises performing one of:(i) a comparison of an elapsed time for drying the wood collection inthe kiln with a predetermined elapsed time limit for drying thecollection in the kiln, (ii) a comparison of a humidity in the kiln witha humidity threshold, or (iii) a comparison of an impedance for theportion of the wood collection with an impedance threshold; obtaining,when the predetermined condition evaluates to a predetermined result,information for a second time limit different from the first time limit;restarting the timer and using the information for activating the timerto determine when the second time limit is exceeded; and wirelesslytransmitting a second instance of the data to the stationary device, viathe wireless transmitter, when the second time limit is exceeded;wherein for conserving the batteries, the first time limit is longerthan the second time limit.
 21. The method of claim 20, wherein thetimer outputs a notification when the first time limit is exceeded. 22.The method of claim 20, wherein the first time limit is at least twicethe duration of the second time limit.
 23. The method of claim 20,wherein the using includes replacing the first time limit with thesecond time limit.
 24. The method of claim 20, further including:obtaining an instance of the data during the first time limit;determining a value indicative of a change between the instance and aprevious instance of the data from a previous iteration of the method;comparing the value to a predetermined change related conditionindicative of particular changes between instances of the data; andwirelessly transmitting the instance to the stationary device, via thewireless transmitter, when the comparing yields a first resultindicative of the predetermined change related condition occurringbetween the one instance and the previous instance, and not wirelesslytransmitting the instance when the comparing yields a second resultindicative of the predetermined change related condition not occurringbetween the one instance and the previous instance.
 25. The method ofclaim 24, wherein the predetermined change related condition includes athreshold for determining whether a temperature change between the oneinstance and the previous instance is out of a range corresponding withthe threshold, and wireless transmitting the one instance to thestationary device when the temperature change is out of the range. 26.The method of claim 24, wherein the predetermined change relatedcondition includes a threshold for determining whether a humidity changebetween the one instance and the previous instance is out of a rangecorresponding with the threshold, and wireless transmitting the oneinstance to the stationary device when the humidity change is out of therange.
 27. The method of claim 24, wherein the predetermined changerelated condition includes a threshold for determining whether acapacitance change in the circuit between the one instance and theprevious instance is out of a range corresponding with the threshold,and wireless transmitting the one instance to the device capacitancechange is out of the range.
 28. The method of claim 24, wherein thepredetermined change related condition includes a threshold fordetermining whether a resistance change in the circuit between the oneinstance and the previous instance is out of a range corresponding withthe threshold, and wireless transmitting the one instance to the devicewhen the resistance change is out of the range.
 29. The method of claim20, wherein the evaluating comprises comparing an elapsed time fordrying the collection in the kiln with a predetermined elapsed timelimit for drying the collection in the kiln.
 30. The method of claim 20,wherein the evaluating comprises comparing the humidity in the kiln witha humidity threshold.
 31. The method of claim 20, wherein the evaluatingcomprises comparing the impedance for the portion of the collection withan impedance threshold.
 32. The method of claim 20, further includingusing the stationary device as an intermediate wireless device forproviding communications between a controller for controlling the dryingof the collection in the kiln, the intermediate wireless device forwirelessly communicating with a second sensor.
 33. The method of claim20 further including using the stationary device as an intermediatewireless device for providing communications between a controller forcontrolling the drying of the collection and the sensor, wherein thecontroller accesses data for locating the sensor within the collectionor within the kiln.
 34. The method of claim 33, wherein the controllerselectively activates or deactivates the sensor dependent upon itslocation.
 35. The method of claim 34, wherein the location of the sensoris relative to one or more other wireless sensors in the wood collectionor in the kiln.
 36. A wireless sensor for monitoring the moisturecontent of a collection of wood members being dried in a kiln, the kilnoperable for applying heat, and air circulation for drying the woodcollection to a specified moisture content, wherein the wireless sensoris in operable contact with the wood collection for forming anelectrical circuit with the wood collection, wherein the circuitadditionally includes two spaced apart conductive plates positionedwithin the wood collection, and wherein the sensor and the circuit areconfigured to establish capacitance and resistance of a water content ofa portion of the wood collection, the portion residing between thespaced apart conductive plates; the sensor comprising: one or morebatteries for electrically powering the sensor; a wireless transmitterfor wirelessly communicating with a stationary device, the wirelesscommunications including transmissions by the transmitter of datarelated to the water content of the portion of the wood collection, thedata including measurements of each of the capacitance and resistance,measurements of the humidity in the kiln, and measurements of atemperature in the kiln; a processor for iteratively: (i) obtaining oneof the measurements of the capacitance, one of the measurement of theresistance, one of the measurements of the humidity, and one of themeasurements of the temperature, and (ii) providing the one measurementof each of: the capacitance, resistance, humidity and temperature to thewireless transmitter for wirelessly transmitting as an instance of thedata; a timer for determining when a first time limit is exceeded;wherein the wireless transmitter is configured to wirelessly transmit afirst instance of the data to the device when the first time limit isexceeded; wherein the processor is configured to evaluate apredetermined condition by a performance of one of: (i) a comparison ofan elapsed time for drying the collection in the kiln with apredetermined elapsed time limit for drying the wood collection in thekiln, (ii) a comparison of a humidity in the kiln with a humiditythreshold, or (iii) a comparison of an impedance for the portion of thewood collection with an impedance threshold; wherein the processor isconfigured to obtain, based on a result of the performance, informationfor a second time limit different from the first time limit; wherein theprocessor is configured to restart the timer and use the information foractivating the timer to determine when the second time limit isexceeded; wherein the wireless transmitter is configured to wirelesslytransmit a second instance of the data to the stationary device when thesecond time limit is exceeded; wherein for conserving the batteries, thefirst time limit is longer than the second time limit.
 37. The sensor ofclaim 36, wherein one of the instances of the data is obtained by theprocessor during the first time limit; wherein the processor isconfigured to obtain a value indicative of a change between the oneinstance and a previous instance of the data from a previous iteration;wherein the processor is configured to compare the value to apredetermined change related condition for identifying specific changesbetween instances of the data, and thereby obtains one of: a firstresult indicative of the predetermined change related conditionoccurring between the one instance and the previous instance, and asecond result indicative of the predetermined change related conditionnot occurring between the one instance and the previous instance; andwherein the wireless transmitter is configured to wirelessly transmitthe instance to the stationary device when the first result is obtained,and not wirelessly transmit the instance when second result is obtained.38. The sensor of claim 36, further including a component that isconfigured to persistently store an identifier, wherein the identifieris retrieved from the component and included in each instance of thedata for distinguishing wireless transmissions of the instances fromwireless transmissions not originating with the sensor.
 39. A wirelesssensor for monitoring the moisture content of a collection of woodmembers being dried in a kiln, the kiln operable for applying heat, andair circulation for drying the wood collection to a specified moisturecontent, wherein the wireless sensor is in operable contact with thewood collection for forming an electrical circuit with the woodcollection, wherein the circuit additionally includes two spaced apartconductive plates positioned within the wood collection, and wherein thesensor and the circuit are configured to establish capacitance andresistance of a water content of a portion of the wood collection, theportion residing between the spaced apart conductive plates; the sensorcomprising: one or more batteries for electrically powering the sensor;a wireless transmitter for wirelessly communicating with a stationarydevice, the wireless communications including transmissions by thetransmitter of data related to the water content of the portion of thewood collection, the data including measurements of each of thecapacitance and resistance, measurements of the humidity in the kiln,and measurements of a temperature in the kiln; a processor foriteratively: (i) obtaining one of the measurements of the capacitance,one of the measurement of the resistance, one of the measurements of thehumidity, and one of the measurements of the temperature, (ii) providingthe one measurement of each of: the capacitance, resistance, humidityand temperature to the wireless transmitter for wirelessly transmittingas an instance of the data for adjusting a push rate of the woodcollection into the kiln.